The present invention relates to a combine harvester. More particularly this invention concerns a system for metering the recycled-tailings stream in such a harvester.
A standard combine harvester cuts standing crop and threshes it to separate the grain from surrounding husks, stems, dust particles and the like, generically referred to as the straw. After initial threshing and separation of a portion of the straw, the grain still carrying considerable straw is fed to a cleaning mechanism that separates out more of the straw and feeds the grain to the grain tank of the machine.
The material separated by the cleaning mechanism from the grain is referred to as tailings and, while it is mainly straw, includes a certain percentage of grain. If the threshing and cleaning mechanisms are set so as to substantially eliminate grain in these tailings, they will normally work too slowly for efficient harvesting. Thus a certain inefficiency is accepted in the cleaning mechanism.
In order not to lose the valuable grain fraction of the tailings, they are typically recirculated back to the cleaning mechanism, to the intake thresher, or even to a separate rethreshing unit so that the machine has a second chance to separate out the desired grain. Thus the incoming stream of cut crop is separated into three fractionsxe2x80x94the grain, the straw, and the tailingsxe2x80x94and the tailings are reintroduced into the crop stream upstream of the separation stage.
The standard Claas machines route the recycle stream so that the machine operator can actually look at it. This permits an experienced machine operator to adjust various parameters, such as travel speed and sieve spacing, to optimize harvesting efficiency. Even with a very experienced operator, this system is highly inaccurate. A flow that is too large is an indication that the cleaning mechanism is working inefficiently and has the corollary disadvantage of overloading the cleaning mechanism by, in effect, running a too large portion of the crop through it twice. A flow that is to small is normally an indication that the cleaning device is either passing too many impurities or working too slowly. Normally the weight rate of the tailings flow is held to about 5% to 10% of the grain flow into the grain tank.
The combine harvester described in EP 0,463,240 of Paquet eliminates the factor of operator error by automatically metering the flow of the recycle stream and automatically resetting the cleaning mechanism to maintain the desired amount of recycle flow. Similarly German patent documents 2,445,045 of Graeber, 4,138,533 of Allworden, and 196 18 042 of Dalmer propose various arrangements that measure the overall flow, that is mass passed per unit of time, in the recycle conduit in a combine, forage harvester, field chopper, or the like.
All of these system are relatively inefficient in optimizing the efficiency of the harvester. The tailings-recycle stream can seem too big when it actually is mainly straw with a minor fraction of recoverable grain, or can seem quite small when it actually is carrying a considerable amount of recoverable grain. The condition of the crop, its moisture content for example, can vary the effective size and/or mass of the crop stream and thereby cause grain to be wasted or excess tailings to be reprocessed.
It is therefore an object of the present invention to provide an improved system for monitoring the recycled-tailings stream in a crop harvester.
Another object is the provision of such an improved system for monitoring the recycled-tailings stream in a crop harvester which overcomes the above-given disadvantages, that is which accurately determines the real efficiency of the grain separator and provides an output that allows the harvester to be set for maximum grain recovery and minimal straw recycling.
A harvester has a thresher for receiving at an intake a mixture of straw and grain and for separating the mixture into grain, straw, and tailings comprised of mixed grain and straw and a conveyor recirculates a stream of the tailings along a path back to the intake. According to the invention a sensor is positioned in the path and intercepts at least a portion of the stream for counting a number of grains in the portion of the stream passing the sensor.
Thus in accordance with the instant invention the actual volume of the tailings stream is largely ignored. It is the actual count of grains in the tailings stream that is critical. How many grains pass the sensor in a given unit if time is an excellent gauge of how efficiently the harvester is operating since, if it is producing a considerable tailing stream but there is very little recoverable grain in it, the fact that the tailings stream is large does not really signify much. On the other hand if the tailing stream is meager, but is formed in large part by recoverable grain, this fact is important to note when adjusting how the machine operates.
The conveyor includes an elevator for raising the tailings stream to a location above the sensor and for dropping the tailings stream on the sensor. To this end the sensor can simply be constituted basically as a microphone that pings when directly impinged by a hard object, and virtually the only hard objects in the tailings stream are grain kernels. The sensor can be provided at the suction intake where the tailings are initially picked up and conveyed also. It can also be provided in a region where the tailings are projected centrifugally, that is the tailings can actually be thrown against the sensor.
The thresher in accordance with the invention includes a main threshing drum and a cleaning unit downstream therefrom. The conveyor can feed the tailings stream back to the drum. Alternately it can feed it directly to the cleaning unit since there is little in the tailings that really needs the coarse conminution done by the threshing drum at the thresher intake. Alternately the system can have a separate rethresher that the tailings are fed to.
The intake is horizontally elongated and the conveyor includes a housing extending above and parallel to the intake and having an array of downwardly open holes and an auger in the housing for displacing the tailings stream therethrough such that particles of the stream drop through the holes. The sensor is elongated, extends parallel to the housing and intake, and is underneath the holes. These holes can be varied in size by juxtaposing the perforated lower wall of the housing with a slidable sieve that is identically apertured so when the holes of the sieve and housing are perfectly aligned, the holes are of their maximum flow cross section but when the sieve is offset the mesh size is reduced. Appropriate hydraulic, pneumatic, or electric actuators can be used to control the sifting action of the housing lower wall.
The housing according to the invention has an inner end above one end of the intake and an open outer end above a generally central portion of the intake so that any tailings that have not dropped through the holes are ejected by the auger at the open outer end of the housing. Thus there is a sifting action in this distributor housing so that virtually all of the grain in the tailings will drop through the holes before the balance of the tailings is ejected by the auger from the housing end.
The system further has according to the invention a display for displaying the number of grains counted by the sensor. Thus the operator of the machine can determine what action to take when tailings-grain count changes, or at least can monitor what the machine is doing and override if necessary.